FlatMapElements (Google Cloud Dataflow SDK 1.9.1 API)

Google Cloud Dataflow SDK for Java, version 1.9.1

Warning: Dataflow SDK 1.x for Java is unsupported as of October 16, 2018. After August 12, 2020, you can use unsupported SDKs temporarily while you upgrade your pipelines. For more information, see Using an unsupported SDK.

For information on migrating from the 1.x SDK, see Migrating from Dataflow SDK 1.x for Java.

Note: If you are using Cloud Dataflow SDK version 2.x, see the Apache Beam API reference documentation.

com.google.cloud.dataflow.sdk.transforms

Class FlatMapElements<InputT,OutputT>

• java.lang.Object
• • com.google.cloud.dataflow.sdk.transforms.PTransform<PCollection<InputT>,PCollection<OutputT>>
  • • com.google.cloud.dataflow.sdk.transforms.FlatMapElements<InputT,OutputT>

• All Implemented Interfaces:

  HasDisplayData, Serializable

  ---

  
  

  public class FlatMapElements<InputT,OutputT>
  extends PTransform<PCollection<InputT>,PCollection<OutputT>>

  PTransforms for mapping a simple function that returns iterables over the elements of a PCollection and merging the results.

  See Also:

  Serialized Form

• • Nested Class Summary

    Nested Classes 

    Modifier and Type	Class and Description
    static class	FlatMapElements.MissingOutputTypeDescriptor<InputT,OutputT> An intermediate builder for a FlatMapElements transform.

  • Field Summary

    • Fields inherited from class com.google.cloud.dataflow.sdk.transforms.PTransform

      name

  • Method Summary

    All Methods Static Methods Instance Methods Concrete Methods 

    Modifier and Type	Method and Description
    PCollection<OutputT>	apply(PCollection<InputT> input) Applies this PTransform on the given InputT, and returns its Output.
    static <InputT,OutputT> FlatMapElements.MissingOutputTypeDescriptor<InputT,OutputT>	via(SerializableFunction<InputT,? extends Iterable<OutputT>> fn) For a SerializableFunction<InputT, ? extends Iterable<OutputT>> fn, returns a PTransform that applies fn to every element of the input PCollection<InputT> and outputs all of the elements to the output PCollection<OutputT>.
    static <InputT,OutputT> FlatMapElements<InputT,OutputT>	via(SimpleFunction<InputT,? extends Iterable<OutputT>> fn) For a SimpleFunction<InputT, ? extends Iterable<OutputT>> fn, return a PTransform that applies fn to every element of the input PCollection<InputT> and outputs all of the elements to the output PCollection<OutputT>.

    • Methods inherited from class com.google.cloud.dataflow.sdk.transforms.PTransform

      getDefaultOutputCoder, getDefaultOutputCoder, getDefaultOutputCoder, getKindString, getName, populateDisplayData, toString, validate

    • Methods inherited from class java.lang.Object

      clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

• • Method Detail

    • via

      public static <InputT,OutputT> FlatMapElements.MissingOutputTypeDescriptor<InputT,OutputT> via(SerializableFunction<InputT,? extends Iterable<OutputT>> fn)

      For a SerializableFunction<InputT, ? extends Iterable<OutputT>> fn, returns a PTransform that applies fn to every element of the input PCollection<InputT> and outputs all of the elements to the output PCollection<OutputT>.

      Example of use in Java 8:

      
       PCollection<String> words = lines.apply(
           FlatMapElements.via((String line) -> Arrays.asList(line.split(" ")))
               .withOutputType(new TypeDescriptor<String>(){});
       

      In Java 7, the overload via(SimpleFunction) is more concise as the output type descriptor need not be provided.

    • via

      public static <InputT,OutputT> FlatMapElements<InputT,OutputT> via(SimpleFunction<InputT,? extends Iterable<OutputT>> fn)

      For a SimpleFunction<InputT, ? extends Iterable<OutputT>> fn, return a PTransform that applies fn to every element of the input PCollection<InputT> and outputs all of the elements to the output PCollection<OutputT>.

      This overload is intended primarily for use in Java 7. In Java 8, the overload via(SerializableFunction) supports use of lambda for greater concision.

      Example of use in Java 7:

      
       PCollection<String> lines = ...;
       PCollection<String> words = lines.apply(FlatMapElements.via(
           new SimpleFunction<String, List<String>>() {
             public Integer apply(String line) {
               return Arrays.asList(line.split(" "));
             }
           });
       

      To use a Java 8 lambda, see via(SerializableFunction).

    • apply

      public PCollection<OutputT> apply(PCollection<InputT> input)

      Description copied from class: PTransform
      Applies this PTransform on the given InputT, and returns its Output.

      Composite transforms, which are defined in terms of other transforms, should return the output of one of the composed transforms. Non-composite transforms, which do not apply any transforms internally, should return a new unbound output and register evaluators (via backend-specific registration methods).

      The default implementation throws an exception. A derived class must either implement apply, or else each runner must supply a custom implementation via PipelineRunner.apply(com.google.cloud.dataflow.sdk.transforms.PTransform<InputT, OutputT>, InputT).

      Overrides:

      apply in class PTransform<PCollection<InputT>,PCollection<OutputT>>